Variable output voltage selector

ABSTRACT

Variable output voltage selectors are disclosed herein. In one embodiment the two opposite terminals of an output potentiometer are connected individually with adjustable contactors of a pair of variable resistors that are connected in parallel between circuit points of differing constant voltage levels. A separate resistor is series connected with each of the variable resistors so that the resistive path of each of the variable resistors has a different voltage gradient profile. The contactors are ganged so that each traverses a corresponding distance along its resistor so that a variable voltage range can be effected between the contactors. The output pot has an output contactor adjustable to select a voltage level within the range of voltage determined by the position of the contactors of the pair of variable resistors. In another embodiment an output pot is connected between a pair of contactors which are adjustable in ganged relationship along a single resistive path having lengthwise nonlinear resistivity.

United States Patent [72] Inventor Reuben C. Carlson Bloomingdale, Ill.

[21 1 Appl. No 839,166

[22] Filed July 7, 1969 [45] Patented Sept. 7, 1971 [73] Assignee Standard Kolsman Industries Inc.

Melrose Park, Ill.

[54] VARIABLE OUTPUT VOLTAGE SELECTOR Primary Examiner-J. D. Miller Assistant Examiner-Harry E. Moose, .lr.

Attorneys-E. Manning Giles, J. Patrick Cagney and Peter S.

Lucyshyn ABSTRACT: Variable output voltage selectors are disclosed herein. ln one embodiment the two opposite terminals of an output potentiometer are connected individually with adjustable contactors of a pair of variable resistors that are connected in parallel between circuit points of differing constant voltage levels. A separate resistor is series connected with each of the variable resistors so that the resistive path of each of the variable resistors has a different voltage gradient profile. The contactors are ganged so that each traverses a corresponding distance along its resistor so that a variable voltage range can be effected between the contactors. The output pot has an output contactor adjustable to select a voltage level within the range of voltage determined by the position of the contactors of the pair of variable resistors. ln another embodiment an output pot is connected between a pair of contactors which are adjustable in ganged relationship along a single resistive path having lengthwise nonlinear resistivity.

PATENTEDSEP nan $603370 SHEET 1 OF 3 FIG. 1

. INVENTOR FIG. 3 Reuben C. Car/son ATTY.

BATENTEQSEP new SHEET 2 OF 3 FIG. 5

FIG. 4

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INVENTOR Reuben C. Car/son ATTY. n7

FIG. 3A

' PATENTED SEP nan SHEET 3 BF 3 FIG. 9

HM: e90

FIG. 10

FIG. 11

IN VE N TOR Reuben C. Car/son ATTY.

VARIABLE OUTPUT VOLTAGE SELECTOR BACKGROUND OF THE INVENTION The term voltage range" as used has the property of span (absolute difference between two applied voltages) and value (the arithmetical average of two applied voltages).

The present invention relates generally to voltage dividers and, moreparticularly, to a variable voltage device wherein a precise voltage level is selectable from a range of voltage, the span and value of which are simultaneously and proportionately adjustable.

A need exists for an inexpensive variable voltage device capable of providing accurate voltage output over a relatively wide range of voltage without attendant difficulties in precise voltage level selection.

Conventional inexpensive variable voltage devices, such as trimming potentiometers, have serious shortcomings when used to provide wide ranges of voltage in applications requiring precise voltage level selection. In addition to requiring extremely precise positioning of the output tap or contactor relative to the resistive path or element to achieve an exact specified voltage output, such conventional devices exhibit unacceptable contactor noise for many applications.

SUMMARY OF THE INVENTION A variable voltage device in accordance with the present invention includes facilities providing first and second resistive path regions, each of the regions having a different predetermined voltage gradient profile. First and second contactors respectively engage the first and second resistive path regions to determine a voltage range between the contactors and are movable relative to the regions. to vary the voltage range. An output potentiometer is connected between the contactors and has an adjustable output tap to provide a variation in output voltage within the voltage range determined by the relav tive position of the contactors along the resistive path regions.

In one embodiment the first and second resistive path regions each comprise a portion of a separate resistive path each being of substantially uniform lengthwise resistivity.

In another embodiment the first and second path regions comprise portions of a single resistive path having nonuniform lengthwise resistivity.

In the disclosed embodiments, the output potentiometer is rigidly connected between the contactors. A selector mechanism is provided for altering the position of the output tap and, for moving the contactors relative to the resistive path regions when the output voltage is either at the maximum or minimum voltage level within the voltage range.

In one important adaptation of the present invention, a tuning voltage control for controlling the voltage levels applied to a voltage responsive type of television tuner comprises a plurality of variable voltage devices, each device including facilities providing first and second resistive path regions having different predetermined voltage gradient profiles, and first and second contactors respectively engaging the first and second resistive path regions to determine a voltage range between the contactors and movable relative to the resistive path regions to vary the voltage range. A potentiometer having first and second terminals has an adjustable output tap connected to determine the applied voltage at the tuner. A selector mechanism is actuatable to a corresponding number of settings to selectively connect the first and second contactors of each of the devices respectively with the first and second terminals of the potentiometer.

In another arrangement, a tuning voltage control comprises a plurality of variable voltage devices, each including facilities providing first and second resistive path regions having different voltage gradient profiles, first and second contactors respectively engaging and movable along the first and second resistive path regions, and a potentiometer connected between the contactors. A selector mechanism having a corresponding number of settings is actuatable to selectively connect an output tap of the potentiometers individually with a tuning voltage bus which is connected to determine the applied voltage of a voltage responsive tuner.

Other features and advantages of the invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings forming a part of the specification, and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a schematic circuit diagram showing one embodiment of a variable voltage device in accordance with the present invention;

FIGS. 2 and 3 are similar and are elevational views showing structure comprising one example of a variable voltage control of FIG. 1;

FIG. 3A shows a scale and indicator arrangement which can be used with the control of FIGS. 2 and 3;

FIG. 4 is a graph depicting the voltage levels of contactors 16, 17 as they are caused to traverse variable resistors R1 and R2 from position AA' to position B-B';

FIG. 5 is an elevational view showing a second example of a variable voltage device of FIG. 1;

FIG. 6 is a schematic diagram of a third example of a variable voltage device of FIG. 1;

FIG. 7 is a schematic circuit diagram of a second embodiment of a variable voltage device in accordance with the present invention;

FIG. 8 is an elevational view showing one example of a variable voltage device of FIG. 7;

FIG. 9 is a graph depicting a typical applied voltage-tofrequency response characteristic curve of a UHF varactordiode television tuner;

FIG. 10 is a schematic and functional circuit diagram of a control incorporating a variable voltage device of the present invention; and

FIG. 11 is a schematic and functional circuit diagram of another control incorporating a variable voltage device in accordance with the present invention.

DETAILED DESCRIPTION Turning now to the drawings, and specifically, to FIG. I, there is shown a schematic circuit diagram of one embodiment of a variable voltage device in accordance with the present invention.

In FIG. 1 the device is shown having a circuit configuration wherein a pair of conventional inexpensive linear potentiometers or variable resistors R1 and R2 areconnected in parallel between a source of voltage (at line 10) and ground. More accurately, the circuit configuration provides first and second resistive path regions, respectively comprising region A-B of the resistive path of variable resistor R1 and region A'-B' of the resistive path of variable resistor R2. Each of the regions A-B and A-B is provided with different predetermined voltage gradient profiles by providing a resistor R3 in series between variable resistor R1 and line 10 and by providing resistor R1 in series between variable resistor R2 and ground.

A pair of contactors l6, 17 are respectively engageable with the resistive path regions A-B, A'-B' and, as indicated by the dotted line in FIG. I, are ganged for corresponding movement lengthwise along the path regions. Because of the different voltage gradient profiles, a voltage range will exist between contactors 16, I7 and such voltage range will be caused to vary as the contactors 16, 17 are caused to move in ganged relationship relative to the resistive path regions A-B, A'B'. An output potentiometer R4 is shown connected between contactors 16,.17 so that the voltage range between the contactors will substantially determine the voltage range over which potentiometer R4 will operate. Potentiometer R4 is shown to include an output tap 19 that is adjustable to provide a variation in output voltage within the voltage range that is determined by the relative location of contactors 16, 17 along their respective resistive path regions.

If the impedance of resistor R3 is greater than the impedance of resistor R5, the voltage range between contactors l6, 17 will be greatest when the contactors are at position A- A and will diminish gradually both in span and in value as the contactors traverse the path regions to a minimum range at positions B-B'. Thus, the output voltage applied to line 20 can be made to vary substantially from the level of voltage at position A to the level of voltage at position B through adjustment of contactors 16, 17 from position A-A' to position 8-- B and through adjustment of output tap 19 from position C to C'.

FIG. 4 graphically depicts the voltage levels at contactors 16, 17 as they are caused to traverse in ganged relationship their respective resistive path regions A43 and AB, where the circuit configuration has 30 volts applied to line 10 and where Rl=R2=50 kilohms, R3=33 kilohms, R5=l .8 kilohms, and R4=20 kilohms. When contactors 16, 17 are at the position A-A', the potentiometer or variable resistor R4 is adjustable to provide voltage levels approximately between 24-30 volts. As the contactors traverse their respective resistive path regions to position B-B', variable resistor R4 is adjustable to provide ranges of voltage having progressively smaller spans and values. At position B-B', variable resistor R4 is adjustable approximately between -1 volts.

While the span of the operating range of the device in the above example is approximately 30 volts, the greatest voltage range span across variable resistor R4 is approximately 6 volts. Thus, it will be appreciated that such permits a relatively high degree of accuracy in output voltage selection without resort to exceedingly fine mechanical adjustment of output tap 19 of variable resistor R4. Further, it will be appreciated that such materially reduces contactor noise and that these characteristics are obtainable without the use of expensive precision potentiometers.

Where resistors R3 and R have substantially the same impedances the span of the voltage range across variable resistor R4 will be substantially constant as contactors 16, I7 traverse their respective resistive path regions. Given the requirements posed by an application, a person skilled in the art can easily tailor the impedances of the various elements of the circuit of FIG. 1 to get the results desired.

Turning to FIGS. 2 and 3, there is shown one embodiment of the variable voltage circuit of FIG. 1 wherein the variable resistors R1, R2 and R4 are of the conventional inexpensive linear-slide type. Each of the variable resistors are of the same basic construction well known in the art. Briefly, referring specifically to variable resistor R1 of FIG. 2, each comprises a rectangularly shaped base of insulation material having a film of resistive material 61 bounded at each end by a film of conductive material 62. A plastic slider 16A carries contactor 16 in yielding engagement with the resistive material 61 along the resistive path.

Variable resistors R1 and R2 are secured to a mounting panel 22 in edge-to-edge straight line extending relation. Contactors 16, 17 are welded to opposite terminal ends 23, 24 of variable resistor R4 so that variable resistor R4 is supported therebetween above the mounting panel 22. The output tap 19 of variable resistor R4 has a wiper contact 25 slidably engaging a conductive strip 26 that is mounted directly to panel 22 and connected to output voltage line 20. The slider 19A supporting contactor 19 is secured to a continuous pulley line 27 which, in turn, is driven by a control shaft 28 that extends through and is suitably secured to panel 22. A control knob 29 is secured to shaft 28 for actuating the pulley. Rotation of knob 29 in the direction of the arrow (FIG. 2) causes slider 19A to translate along the resistive path of variable resistor R4 towards position C. Upon reaching position C' further movement of slider 19A along resistor R4 will be impeded by terminal 23 and further rotation of knob 29 will cause translation of the entire variable resistor R4 towards the right, thereby causing contactors 16, 17 of variable resistors R1 and R2 to translate in ganged relationship towards positions B and B (FIG. 3).

Referring to FIG. 3A there is shown a scale and indicator arrangement which may be used with the device of FIGS. 2 and 3. Thus, FIG. 3A shows a disclike scale 68 having a number of voltage levels calibrated in accordance with the characteristics of the particular variable voltage device to be used. A bushing 65 carries a pointer 67 and is mounted on the control shaft 28 at a position between the scale 68 and control knob 29. Bushing 65 is provided with an annular slot 65A through which extends a pin 66 that is connected to control shaft 28. Rotation of the control knob 29 causes pin 66 to rotate along with shaft 28 within slot 65A. Upon reaching an end of slot 65A further rotation of control knob 29 will cause pin 66 to rotate bushing 65 and hence, the indicating pointer 67. The angular length of slot 65A is such that rotation of control knob 29 through a corresponding number of degrees results in movement of output tap 19 from position C to C'. Thus, initial rotation of the control knob 29 of FIG. 3A in a counterclockwise direction causes movement of output tap 19 until it reaches position C, at which time pin 66 reaches one end of slot 65A, and continued rotation clockwise of knob 29 causes contactor 16, 17 to translate towards position B-B' as indicated by the movement of pointer 67 in a counterclockwise direction. Thus, for example, if an output voltage level of 19.5 volts is desired, the operator need only clockwise rotate knob 29 until the indicator is directed to approximately digit 20 of the scale and then rotate knob 29 counterclockwise to fine tune" the output voltage. The actual output voltage can be determined through use of conventional meter (not shown).

FIG. 5 shows another embodiment of the variable voltage circuit of FIG. 1 which differs from the device of FIGS. 2 and 3 primarily in that the variable resistor R4 is of the conventional inexpensive rotary tap type. In FIG. 5, conventional linear slide type variable resistors R1 and R2 are shown aligned in parallel side-by-side relationship. Variable resistor R4 includes a base 32 of insulating material having a connect-' ing member 39 integral therewith. The vase 32 spans and rests directly upon resistors R1 and R2 and has a transverse bridge 39 mechanically secured to sliders 16A, 17A. The resistive path 33 of variable resistor R4 is annular in shape and has its opposite end regions respectively electrically connected with contactors 16, 17. An output tap or contactor I9 is mounted for rotary adjustment along resistive path 33 in accordance with rotation of gear 37. In order to control the output voltage level, a worm gear 38 drives gear 37 Thus, as worm gear 38 is rotated in one direction, tap 19 rotates along resistive path 33 until it reaches one of the end stops 35, 36. Once tap 19 reaches one of the stops, further rotation of worm gear 38 in the same direction will cause the entire variable resistor R4 to translate parallel to the worm gear 38 and resistors R1, R2 thereby causing slider 16A, 17A to traverse in ganged relationship along the resistive path regions of variable resistors R1 and R2.

Still another embodiment of the variable voltage circuit of FIG. 1 is shown in FIG. 6 wherein each of the variable resistors R1, R2 and R4 are of the rotary-tap type. In FIG. 6, variable resistors R1 and R2 are mounted on opposite sides of the mounting panel 22. A key slot 43 is provided so that the contactors of variable resistors R1 and R2 can be simultaneously positioned relative to their respective resistance paths. The contactors of variable resistors R1 and R2 are connected through lines 40, 41 to the opposite end regions of the resistive path of variable resistor R4. 2

FIG. 7 is a schematic diagram of another circuit arrangement of a variable voltage device in accordance with the present invention. In FIG. 7 the device is shown having a circuit configuration wherein a single resistive path 54 provides first and second resistive path regions A-B and A-B'. As shown, resistive path 54 is of lengthwise nonlinear resistivity so that the voltage gradient profiles of regions A-B and A-B differ. A pair of contactors 52, 53 respectively engage the first and second path regions to determine a voltage range between the contactors and are movable relative to the path regions in ganged relationship to vary both the span and value of the voltage range. An output potentiometer R4 is connected between contactors 52, 53 to provide a variation in output voltage within the voltage range determined by contactors 52, 53.

FIG. 8 shows an embodiment of the variable voltage circuit of FIG. 7 and comprises a conventional inexpensive linear slide-type-variable resistor 55 wherein the film of resistive material 54 has been shaved to provide for lengthwise nonuniform resistivity. Contactors 52 and 53 are mounted for engagement with the resistive material 54 by means of conventional slides 52A and 53A. In a manner similar to that of the device of FIG. 5, a rotary tap-type-variable resistor R4 has the opposite ends of its resistive path respectively connected with contactors 52, 53 and has its base portion rigidly connected to each of the sliders 52A, 53A so that transverse movement of the variable resistor R along the resistive path 54 produces corresponding movement of contactors 52, 53.

The variable voltage device of the present invention is particularly suitable as a channel selector control for radio and television receivers incorporating voltage responsive types of tuners. FIG. 9 shows a tuning voltage-to-frequency response curve characterizing a typical voltage responsive UHF television tuner. It can be seen that a relatively small variation in voltage is required for tuning to adjacent UHF channels at the lower frequency levels whereas a relatively large variation of voltage is required to tune to adjacent channels at the higher frequency levels.

Comparing FIGS. 4 and 9, it will be noted that the span of the voltage range between contactors I6, 17 varys directly with the value of the voltage ranges. Thus, the voltage range across the resistive path of variable resistor R4 can be adjusted to any predetermined one of a plurality of voltage ranges, each range being such as to effect a substantially constant span frequency range response in the tuner of a television receiver. By proper selection of impedances for variable resistors R1, R2 and R4 and resistors R3 and R5 of the circuit of FIG. 1, the contactors l6, 17, can be adjusted to predetermined intermediate positions between regions A-A' and BB, each position providing a voltage range across variable resistor R4 that includes the voltage level determination of a particular UHF channel. Since assigned UHF channel frequencies are separated by at least 36 MHz., if the frequency range response of the tuner at any position between positions A-A' and B- B is less than 36 MHz., the variable resistor R4 can be utilized in its entirety for fine tuning of individual UHF channels. Such result is obtained, for example, in a circuit configuration of FIG. 1 where 25 volts is fed along line and where R1=l3.8 kilohms, R2=I0 kilohms, R3=33 kilohms, R4=20 kilohms and R5=820 kilohms.

It will be noted that utilization of the device of the present invention as a control for a voltage-responsive television tuner requires extremely low current bleeding along output line 20, which dictates the use of the relatively high impedances above. In the circuit configuration of the above example, the bleeder current is on the order ofa couple of milliamperes.

Turning to FIG. 10 there is shown an example of the manner by which the variable voltage device of the present invention can be adapted to provide a control of inexpensive construction for use with a television tuner T. As shown, four of the variable voltage devices of FIG. 1 are connected in parallel and have their output voltage lines selectively connectable to a tuning voltage bus 20A for determining the applied voltage at a UHF tuner section 22. In the control of FIG. 10, the contactors l6, 17 of each of the variable voltage devices are individually preset to provide a predetermined range of voltage across the corresponding variable resistor R4 and each of the devices has its output tap l9 preset to provide a predetermined level ofoutput voltage in accordance with a single UHF frequency channel. Thus, the control of FIG. 10 can be used to select four UHF channels by means of a detented channel selector mechanism S.

FIG. 11 is a further example of a control incorporating a variable voltage device of the present invention. In FIG. 11 a selector mechanism S selectively connects each of four sets of contactors 16, 17 with a single output potentiometer R4. Potentiometer R4 has an adjustable tap 19 connected to an output voltage line 20 that is connected to determine the applied voltage at a tuner section T. In FIG. 11 each of the four sets of contactors l6, 17 are individually preset to determine a predetermined range of voltage across variable resistor R4 that includes a level of output voltage in accordance with a single UHF channel frequency. The embodiment of FIG. 11 has the advantage over the embodiment of FIG. 10 of requiring less parts, however it requires fine tuning each time a different channel is selected.

Thus, while preferred constructional features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

What is claimed is:

l. A variable voltage control comprising a pair of potentiometers each having a shiftable tap, circuit means connecting said potentiometers in parallel branches and including a resistor connected in series with one of said potentiometers to establish different sets of predetermined voltage levels at each potentiometer, an output potentiometer shiftable in ganged relation with said taps and electrically connected across said taps to establish a range of output voltage in accordance with the instantaneous position of said taps, said output potentiometer having a shiftable tap operable between spaced stops for selecting an output voltage level within said range, and drive mechanism actuatable to shift the last-named tap and thereby to shift said output potentiometer after the last-named tap engages either of said stops.

2. A variable voltage control according to claim I wherein said pair of potentiometers comprise first and second variable resistors having linearly adjustable contactors.

3. A variable voltage control according to claim 2 and further including means mounting said resistors in edge-toedge linearly extending relation, said output potentiometer being linearly shiftable in parallel relation relative to said resistors.

4. A variable voltage control according to claim 2 and further including means mounting said resistors in parallel side-by-side relation, said output potentiometer being linearly shiftable in parallel relation relative to said resistors.

5. A variable voltage control according to claim 3 wherein said output potentiometer comprises a third variable resistor having a linearly adjustable contactor.

6. A variable voltage control according to claim 4 wherein said output potentiometer comprises a variable resistor having a rotary adjustable contactor.

7 A variable voltage device comprising circuit means providing first and second resistive path regions, each of said regions having a different predetermined voltage gradient profile, first and second contactors respectively engageable with said first and second resistive path regions to determine a voltage range between said contactors and moveable in ganged relation along said resistive path regions to vary said voltage range, and an output potentiometer connected between said contactors having an adjustable output tap to provide a variation in output voltage within the voltage range determined by said contactors, means for adjusting said output tap, said last-named means being operable to move said contactors relative to said resistive path regions when said output voltage is either the maximum or minimum voltage level within said voltage range.

8. A variable voltage device comprising circuit means providing first and second resistive path regions, each of said regions having a different predetermined voltage gradient between said contactors having an adjustable output tap for selecting a voltage level within the voltage range determined by said contactors, selector means for altering said output tap,

said adjustable means being responsive to said selector means for varying said voltage range. 

1. A variable voltage control comprising a pair of potentiometers each having a shiftable tap, circuit means connecting said potentiometers in parallel branches and including a resistor connected in series with one of said potentiometers to establish different sets of predetermined voltage levels at each potentiometer, an output potentiometer shiftable in ganged relation with said taps and electrically connected across said taps to establish a range of output voltage in accordance with the instantaneous position of said taps, said output potentiometer having a shiftable tap operable between spaced stops for selecting an output voltage level within said range, and drive mechanism actuatable to shift the last-named tap and thereby to shift said output potentiometer after the last-named tap engages either of said stops.
 2. A variable voltage control according to claim 1 wherein said pair of potentiometers comprise first and second variable resistors having linearly adjustable contactors.
 3. A variable voltage control according to claim 2 and further including means mounting said resistors in edge-to-edge linearly extending relation, said output potentiometer being linearly shiftable in parallel relation relative to said resistors.
 4. A variable voltage control according to claim 2 and further including means mounting said resistors in parallel side-by-side relation, said output potentiometer being linearly shiftable in parallel relation relative to said resistors.
 5. A variable voltage control according to claim 3 wherein said output potentiometer comprises a third variable resistor having a linearly adjustable contactor.
 6. A variable voltage control according to claim 4 wherein said output potentiometer comprises a variable resistor having a rotary adjustable contactor. 7 A variable voltage device comprising circuit means providing first and second resistive path regions, each of said regions having a different predetermined voltage gradient profile, first and second contactors respectively engageable with said first and second resistive path regions to determine a voltage range between said contactors and moveable in ganged relation along said resistive path regions to vary said voltage range, and an output potentiometer connected between said contactors having an adjustable output tap to provide a variation in output voltage within the voltage range determined by said contactors, means for adjusting said output tap, said last-named means being operable to move said contactors relative to said resistive path regions when said output voltage is either the maximum or minimum voltage level within said voltage range.
 8. A variable voltage device comprising circuit means providing first and second resistive path regions, each of said regions having a different predetermined voltage gradient profile, first and second contactors respectively engageable with said first and second resistive path regions to determine a voltage range between said contactors, adjustable means gang-coupling said contactors for corresponding movement of said contactors relative to said resistive path regions to vary the span of said voltage range directly with the value of said voltage range, and an output potentiometer connected between said contactors having an adjustable output tap for selecting a voltage level within the voltage range determined by said contactors, selector means for altering said output tap, said adjustable means being responsive to said selector means for varying said voltage range. 